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Method of fabricating thinned free-standing metallic hydrogen-selective palladium-bearing membranes and novel pin-hole-free membranes formed thereby

Inactive Publication Date: 2000-08-15
HYDRIP LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

It is yet another object to provide such a method adaptable to partially mask said sheet membrane, thereby thinning only selected portions thereof e.g. inner portions of its surface areas.

Problems solved by technology

The cost and difficulty of the before-mentioned cold-rolling of billets to substantially pinhole-free sheets, however, increases sharply as the sheet thickness decreases.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 2

A sample of annealed Pc60 / Cu40 was placed in and intermittently sealed to a frame apparatus so that only one side of the membrane was etched. By masking the edges, an exposed portion of the membrane was selected one square inch of the central portion, and the initial thickness was 0.001" which enabled the membrane to be free-standing within the frame. One side of the membrane was exposed to 40 ml of "neat" nitric acid under constant agitation at 35.degree. C. for 45 minutes followed by rinsing in water and drying. The amount of material removed or thinning was determined to be approximately 30% by weight of the selected exposed portion or area. Small (7 / 16" diameter) circles were cut from the etched portion and tested for hydrogen flux in a small permeation apparatus at 300.degree. C. and 50 psig hydrogen upstream and 0 psig hydrogen downstream (testing flux on a 0.25 cm.sup.2 membrane area). Again, the initial flux of an as-etched foil membrane was found to be inadequate, namely on...

example 3

Three samples of annealed Pd60 / Cu40 foil measuring 2 in. high by 0.625 in. wide by 0.001 in. thick were hung vertically in a beaker through parallel slits in a Teflon sheet resting on the lip of a 25 ml beaker. The slits were cut to provide a 0.25 in. gap between the foils. The foils were immersed to a depth of approximately 0.75 in. in an electrolyte comprised of 0.7M caCl.sub.2 in dimethylsulfoxide.

The center foil was operated electrochemically at room temperature as an anode using the outer foils as cathodes. A current of 0.036 A was passed for 30 minutes. The weight of material removed by electrochemical thinning was approximately 45% of the weight of the exposed area.

A small circle of this thinned foil was tested in the permeation apparatus under conditions described in Example 2. Initial hydrogen flux was found to be inadequate, namely 1.4 cc / cm.sup.2 -min based on thinning from 0.001 in. to 0.00055 in. (i.e. by 55%). Any subsequent decline in flux was changed back to cc / cm.su...

example 4

Example 3 was repeated using three new samples of annealed Pd60 / Cu40 and 1.5M HCl as the electrolyte. The foils were immersed to a depth of approximately 1 in. A current of 0.015 A was passed for 180 minutes. The weight of the material removed by electrochemical thinning was approximately 60% of the weight of the exposed area.

A small circle of this thinned foil was tested in the permeation apparatus under conditions described in Example 2. Initial hydrogen flux was found to be inadequate, namely less than a 1 cc / cm.sup.2 -min. A subsequent activation step of exposing the sample to air for 90 minutes at 300.degree. C. resulted in a hydrogen flux of 67 cc / cm.sup.2 -min. This hydrogen flux corresponds to the expected value of 67 cc / cm.sup.2 -min. This hydrogen flux corresponds to the expected value of 67 cc / cm.sup.2 -min based on thinning from 0.001 in. to 0.0004 in. (i.e. by 40%). Any subsequent decline in flux was changed back to 67 cc / cm.sup.2 -min by reactivation with air. The perm...

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Abstract

A new method of creating thin free-standing pin hole-free hydrogen-selective palladium-bearing membranes that comprises thinning cold-rolled membranes by chemical etching or electrochemically electrolyzing of at least one membrane surface, and novel membranes produced thereby and including membranes with selected portions only thereof so thinned.

Description

This invention relates to palladium-bearing hydrogen-selective metal membranes, and more particularly to methods of producing such in the form of thinned free-standing pin-hole-free sheet foil membranes.As disclosed in our co-pending applications Ser. Nos. 08 / 719,385 and 08 / 880,990, herein incorporated by reference, the art is replete with references to palladium-bearing hydrogen selective membranes and to their use in hydrogen purifiers and reactors and the like. We have stressed in said applications the advantages of palladium alloy membranes in the form of sheet membranes, which have been made significantly thinner than the walls of the commonly used small-diameter tubular membranes. The result has been improved hydrogen permeation as well as significant palladium savings.As used at times in this specification and the appended claims, the term "hydrogen selective palladium-bearing metal" is intended to embrace palladium metal or a hydrogen selective palladium alloy, and the term ...

Claims

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Application Information

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IPC IPC(8): B01D35/06C23F1/02C23F1/04C22F1/14C22B11/00
CPCB01D35/06C22B11/00C22F1/14C23F1/04
Inventor JUDA, WALTERKRUEGER, CHARLES W.BOMBARD, R. TODD
Owner HYDRIP LLC
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